VM: Interesting thing about the Pirelli stories today is the tire pressure recommendation rather radical. 5psi higher is huge. I can’t find the justification for that either. The 0.5 degree camber change is justified as per the prior Pirelli pre-Monza press release.VM: If anyone finds some technical justification on 5psi over inflation, let me know… I’m curious about it.

Mattpt55: Well, basic physics says higher pressure should equal lower rolling resistance, therefore lower temps but less suspension benefitMattpt55: also better fuel economyMattpt55: Just had a thought. Wonder if exceptional number of cuts due to lots of 4 wheel off driving at Spa. If we take the normal circuit and guess that only 2 wheels off then simply having all 4 off at corner doubles chance of off line debris pickup

VM: Higher pressure equals smaller footprint. And the tread will “crown” which means primary work (footprint) is done by middle of tread. It’s very strange, and unjustified technically. AFAIK, it’s unjustified. If my supposition is correct, Pirelli are very gun shy at the moment.VM: Guessing the tires will wear a little sooner due to lesser footprint, to ensure goal of 2 to 3 pit-stops, but not sure. But 5psi is rather radical. Only Hamilton has the courage to call Pirelli on this, which is also interesting.

Mattpt55: OK going off bike tyres about which I know more, lower pressures equal better grip softer ride and more chance of pinch flat if you hit large enough edge.

TD: When you are in front, change is bad. Lewis wants status quo until victory is secured.

Mattpt55: Tread will only crown I would think if they tyre is vastly over-inflatedMattpt55: so the advantage would be less resistance due to smaller contact patch and greater resistance to the sort of damage kerbs do when struck. Perhaps lifting sidewall will help protect the tyres from lateral energy loads of that sortMattpt55: I’m thinking arches in architecture being better at distributing load

VM: Footprint changes with changes as small as 0.5 psi. You control the footprint shape with the pressure.VM: OK, but let’s be clear about the damage curbs will do… Pirelli did a fairly thorough analysis of the tire structures from Spa and found no damage to the structures of the tires. They also found the rubber itself was holding up. The only problem was the tires being cut by debris.

Mattpt55: Right, but is the change linear with pressure? I would think the amount of change would be more tied to the sidewall constructionMattpt55: Perhaps they were concerned about tyres and bodywork. I know Mercedes ran flo viz to see and the tyres weren’t touching but it did look awfully close on some of those slo mo shotsVM: So over inflating the tires is unrelated to what happened at Spa except if it forces faster wear to ensure no team gambles on a single stopper… It’s a rather radical action to take to force a 2 to 3 stopper to my mind.

Mattpt55: I suppose they probably have several different recs depending on parameter they wish to optimize

TD: There were also several curbs added and removed over the course of the weekend. A tiny piece of metal sticking up from a piece of rebar could go virtually unseen. Either the pressure in the tires, it could even be a fraction of an inch below the track surface, and when the asphalt compresses, it would expose the metal.

Mattpt55: And it may be a bit of a reach to say wholly unrelated to Spa. They may have seen indications in data at high speed that they wish to have greater margins for in MonzaMattpt55: But as far as publicly, then yeah

VM: So frustrated with F1 right now because of BS like this, and track limits issues… In this case it appears Pirelli is taking advantage of the situation to force 2 to 3 stoppers by crowning the tires. That comes from reading books on chassis tuning, and tuning a race car and some karts…VM: But no one is talking about the technical merits of this. Perhaps Ted’s notebook, or someone will expose this during the weekend.

TD: http://article.sapub.org/10.5923.j.ijtte.20130202.01.htmlTD:

TD: According to that article, braking distances will increase.

VM: I think that’s the biggest.VM: So what we may expect would be lower corner speeds, longer brake zones, and tires wearing in the middle of the tread. Candidly it may make this race more exciting.

Mattpt55: But not as exciting as randomly exploding tyres

VM: Wow! Pirelli is blowing up Monza. Now we have this amazing statement:

VM: That was FOM saying Pirelli has done what we asked, and thank you for that. Means negotiations must be entertaining behind closed doors between FOM and Pirelli.VM: Then we have team engineers telling Pirelli BS on over-inflating by 5psi. So Pirelli has backed down…

Pirelli – Hey guys, you know these tyres you have been using all year long?
Teams – Yeah, sure. What about them?
Pirelli – Huh, well, nothing, but we want you to limit camber and pressure settings because, ah, well, safety.
Teams – So that means we have been using them wrong for months and months and only now has it become an issue.
Pirelli – Yeah. Now excuse me, Bernie and us have an ass kissing appointment.

What we don’t know is how much influence the teams had on the original ‘recommendations’. It could well be that Pirelli have found themselves pushed downwards by the teams to the point where things are genuinely unsafe and have finally had enough.

Will be interesting to see how it shakes things up though and maybe this is another thing to throw in to the mix to spice the season up – as well as tyre compounds varying per race they vary the pressure and camber settings. I’m sure some cars will react better than others.

a long time ago for sure as an amateur racer/hill climber/sololl/track day competitor… running a legal FF Titan MkV and then modified to a low level FAtlantic with the Lotus Twin Cam and then modified to a pretty top notch FAtlantic spec. me n my partner took turns on the racing side and both drove on the other events. with NO computers, no g meters, no GPS, no ability to change up the setting during a lap, we BOTH could and DID make minute changes to settings – MOSTLY equaling 1/4 Lb tire pressure changes to tire pressure. a mere 1/4 Lb up or down change in tire pressure on all 4 corners meant the difference between hero and zero we did add about 4 lbs to high speed race long high speed events!!
seat of the pants/HP calculator/slide rule/protractor/compass/ruler/bathroom scales/graph paper/ manually-calculated log book/quality analog stop watch and quality analog tire pressure gage always made the day!!
and you will gasp when I tell you I ran the softest dirt track compound by McCreary tire for a full season – including Nelson Ledges, Mid Ohio, Mosport,, the Glen and .a few hillclimb/sololl events!
so, a 5 lb variation in tire pressure is MASSIVELY incomprehensible to me on any and all levels of idiocy!!!
I get that I had zero aero to deal with, but this simply does not compute…

BTW, the low speed events saw tire pressures at about 11PSA fronts and 13 PSI rears – increased about 4 PSI for high speed races – those roughly equal to Spa and Silverstone for a similar class… just saying…

rightly or wrongly, I have never been a fan of Pirelli.
I remember ll the way back to I think 1973 [?] when they had the CN-36 tire used by so many sololl autocrossers. fast for sure, but lasted like 2 Sololl events (~5 miles) b4 becoming bald and throw-away rubber.
not my cup of tea…

I think it’s more complex than contact patch, crowning, braking distances, etc. F1 cars run extremely stiff suspensions and effectively use sidewall flex as a spring. I think increasing the pressure 4# or 5# (about 20%!!) or whatever will make life very difficult for the teams, as they have factored the sidewalls into the setup equation and suspension design. It will be difficult to change things overnight. Might be an interesting race though.

Great points. It’ll be interesting to see during the race how well each team has adjusted during the weekend to this change. Should be apparent in lines, (who uses or avoids curbs), and corner speeds (particularly apex and exit).

Frankly I like everything Pirelli are doing here. Longer braking zones, less footprint, more rigidity, all good. Now let’s see some pressure put onto Charlie to enforce track limits properly, or at all for that matter.

Pirelli are just firing a warning shot across the team’s bows. ‘You complain about safety – this is the result’. And they have their new medal of honour and transcript of commendation from Mr. F1 – at this moment, they can flex their muscle

Shouldn’t the FIA be the ones giving out medals and safety assurances? Are they even doing anything at all? I used to think Max and Bernie were a bad pair, but not it seems that having Bernie roam free actually makes it worse. Maybe my memory is naturally romanticizing the past, but still…

Too simplistic to link tyre pressure to shape, whether in static or dynamic situations. Construction is the key element. It would be easy to create a tyre tread that always has a flat tread/road interface. Think of run flat tyres. F1 tyres tend to deflect the sidewall rather than the tread, when hitting an obstacle, and suspension compliance is mostly from the tyre sidewall. Lateral and longitudinal forces on the tyre from acceleration and cornering can be approx 3-5G. Depending on the car mass, it means tonnes of force. So offtrack excursions, and hitting kerbs is potentially damaging. What looks like a relatively smooth edge, is somewhat different when you impact with a few tonnes of force, over a small point loading. The AMuS photo from Spa, showing severe sidewall rippling, could be a pointer to people running tyres to close to the edge of the operating envelope. That rippling would cause lamination failure at the edge of the tyre, which is what really happened. This is often seen on under inflated truck tyres, which loose their tread and the tyre explodes. Another thing to consider when changing the pressure and the resultant shape change, is the effect on aerodynamics.

Will extra tyres pressure effect ride height and will it have an effect when the car is fully aero-loaded, as the tyres won’t squash down as much if they have more pressure in, there seems to be multiple knock-on issues raised by Pirelli’s ‘aggressive’ choices.